1. Field of the Invention
The present invention relates to a method for controlling an internal combustion engine using a model based control algorithm, and in particular an internal combustion engine having an exhaust gas recirculation (EGR) and/or a variable geometry turbocharger (VGT) system.
2. Background Art
Internal combustion engines, and in particular, compression ignition (or diesel) engines have a wide variety of applications including passenger vehicles, marine vessels, earth-moving and construction equipment, stationary generators, and on-highway trucks, among others.
Internal combustion engines may include exhaust gas recirculation (EGR) systems and/or variable geometry turbocharger (VGT) systems. Conventional EGR and VGT control systems utilize PID (i.e., proportional, integral, derivative) based closed loop electronic controllers. Such conventional controllers generally perform poorly when the engine is operating under transient conditions (e.g., up and down hills, in response to a varying load, idle to rapid acceleration operation, intermittent workpiece characteristics for power takeoff driven applications, etc.). The poor responsiveness may be attributed to the relative sluggishness of air systems. That is, a modification to a controlled parameter does not generally cause an immediate change in an air system of an internal combustion engine. In the case of a PID based controller, the delay between the modification of the controlled parameter and the detection of a change in the system generally results in oscillation around a desired setpoint. The oscillation may be reduced or eliminated by reducing the responsiveness of the PID algorithm. However, reducing the responsiveness generally provides inadequate performance when the system is operating in a transient state.
Thus, there exists a need and an opportunity for an improved method for EGR and/or VGT control.